The invention relates to a device and a method for optically determining a concentration of alcohol and carbohydrates in a liquid sample.
It is known to use optical measuring devices to determine properties such as alcohol (e.g., ethanol) concentrations in consumptive liquids, including, for example, beer, wine, liquor, soft drinks, and low-alcohol or non-alcoholic beer. It is also usually desirable to determine the concentration of other components in the consumptive liquid besides alcohol. In particular, it may be desirable to further determine the concentration of carbohydrates in beer, wine, liquors or the other above mentioned beverages. Said carbohydrates, also called sugars or saccharides, are a specific type of compounds having carbon, hydrogen and oxygen atoms, in which hydrogen and oxygen atoms are present in a 2:1 proportion, the general formula being Cn(H2O)m. The carbohydrate family or sugars also includes monosaccharides, disaccharides, and polysaccharides, among other substances. Examples may include glucose (C6H12O6), maltose (C12H22O11), dextrine (C8H10O5)n, fructose, sucrose, etc. In those cases in which carbohydrates or sugars are mentioned herein, reference is made to the above definition.
EP 1 965 193 A1 discloses a device suitable for determining a concentration of alcohol in which a spectrometer is used to determine light absorption at specific wavelengths. Based on light absorption, the concentration of alcohol in the sample can subsequently be determined.
For example, a liquid sample is exposed by means of a light source and the received light intensity is determined by means of a sensor. Because different components of the liquids exhibit different levels of absorption at different wavelengths, it is possible to determine the concentration of the components in the liquids on the basis of the absorbed light intensity.
The aforesaid device comprises a light source and a sensor, which are arranged to measure the light intensity having at least two wavelengths. Since the light absorption of water and alcohol, and in particular ethanol, hardly differ from each other at the first wavelength, whereas they do differ from each other at the second wavelength, it is possible to determine the concentration of alcohol from the proportion on the basis of said difference. The drawback, however, is the fact that one sensor is used, which must be arranged to capture light at two wavelengths. Thus there can be no question of simultaneous measurements at the different wavelengths. Accordingly, reference is explicitly made to measurements being carried out in succession at the different wavelengths.